Process of making a starch-thickened microwavable food product

ABSTRACT

This invention relates to a process of making a cream-style soup which can be rendered drinkable by microwave heating from a frozen state without recourse to stirring. The soup comprises an aqueous phase substantially uniformly dispersing a starch system and an oleaginous system, the aqueous phase containing at least one dissolved freezing point depressant to provide some free water substantially uniformly dispersed throughout the product. The oleaginous system includes at least one fat in the form of particles of sizes less than 10 microns and starch system comprises at least one starch in a partially gelatinized state and at least one humectant to act as a water activity depressant. The process involves forming a mixture of flavoring components, spray dried oil-based creaming ingredient, granules of at least one acid stable, freeze/thaw stable starch and maltodextrin in water, heating the mixture so that the starch granules are swollen to between 70-80% of their swelling potential, dispensing the mixture into microwavable containers and freezing.

FIELD OF THE INVENTION

This invention relates to a food product and in particular to a frozen, cream-style, starch-containing product which is consumable after microwave preparation without stirring. The invention has particular utility in the production and preparation of a hot drinkable cream-style soup, but can also extend to sweetened dessert products such as custards and milk shakes and to savoury products such as sauces and gravies.

SUMMARY OF THE INVENTION

According to one aspect of the invention a frozen food product comprises an aqueous phase substantially uniformly dispersing a starch system and an oleaginous system, the aqueous phase containing some free water substantially uniformly dispersed throughout the product as a result of freezing point depression of the aqueous phase through the presence in the product of at least one dissolved material acting as freezing point depressant, the oleaginous system including at least one fat in the form of particles of sizes less than 10 microns, and the starch system comprising at least one starch in a partially gelatinised state, at least one humectant being present in the product to act as a water-activity depressant for the starch system.

Suitably the starch(es) in the starch system has/have a gelatinisation temperature between 70° and 75° C. Conveniently the starch(es) constitute(s) from some 2% w/w to 5% w/w of the product. The starch(es) require(s) to be freeze/thaw stable and is/are preferably also acid stable.

Desirably the particles of fat in the oleaginous system have a size of less than 2 microns and conveniently are spray dried on a water activity reducing carrier (e.g. maltodextrin).

Conveniently the product is frozen in volumes of between 100 and 200 ml in at least substantially microwave transparent drinking vessels. Suitably the vessels can be removed from a microwave oven after thawing and heating the product and can be supported with a near-boiling aqueous phase within the vessel in a thermally unprotected hand.

In a preferred form, the product is a volume of 150 ml to 170 ml of frozen cream-style soup which can be transformed into a hot drinkable product of moderate viscosity directly from the frozen state (e.g. at -18° C.) with no stirring after approximately 3 minutes in a microwave oven (e.g. operating at some 2450 megahertz and 600 watts) and comprises (a) a partially gelatinised starch system based on at least one acid stable, freeze/thaw stable, modified waxy maize starch having a gelatinisation temperature at around 75° C., (b) an oleaginous system comprising droplets of less than 10 microns in diameter of hydrogenated vegetable oil, (c) an aqueous phase dispersing the two systems (a) and (b) substantially homogeneously, the aqueous phase including ice particles dispersed in free water and (d) maltodextrin dissolved in the free water to create a substantially continuous carrier phase for systems (a) and (b).

According to a further aspect of this invention, a process for manufacturing the precursor of a recently-thawed drinkable, starch-thickened, cream-style food product, heated from a frozen state without stirring in a microwave oven, comprises forming a homogeneous mixture of product flavouring components, spray dried creaming ingredient based on vegetable oil, granules of at least one acid stable, freeze/thaw stable starch ano maltodextrin in water, heating the mixture to a temperature at which swelling of the starch granules will commence for a time to produce between say 70% and 80% of the total swelling potential of the starch granules, dispensing the mixture into individual containers intended to contain the product while heated in a microwave oven and while subsequently consumed, and freezing the containers and dispensed mixture to a temperature of between -15° and -20° C.

The extent to which the starch granules are swollen prior to freezing will be determined on the basis of the post-freezing microwave heating cycle to which the product will be subjected prior to consumption but the range quoted above will be typical. For a volume of 150 to 170 ml of cream soup subjected to 31/4 minutes of microwave heating from frozen a percentage swelling of some 95% would be typical. A gelatinisation temperature for the starch granules would conveniently be around 75° C.

The proportions of starch(es), fat, flavouring components and the amount and type of maltodextrin used in the mixture will be determined by the end product, but typical proportions for two soup mixes is given hereafter. Whey powder can be added to the starch system if required to modify texture/taste properties of the product.

The creaming ingredient can be a spray dried hydrogenated vegetable oil of droplet size two microns or less on a maltodextrin carrier and can be added in a cold water-based slurry to a hot aqueous mix of the flavouring components. The starch(es) can be added subsequently also in a cold aqueous slurry containing maltodextrin and the heating to swell the starch granules to the required extent is conducted as the final hot processing stage prior to dispensing the mixture into individual portion-sized ready-to-serve containers preparatory to freezing. The use of a liquid creaming ingredient of fat droplet size less than ten microns (and preferably less than two microns) is not ruled out.

Whilst not attempting a full explanation of the processes involved, it is believed that the maltodextrin acts as a humectant or water activity depressant in the aqueous mixture. This has two effects, firstly it prevents further swelling of the starch granules until the temperature during the microwave heating increases to a point where starch granule swelling can be completed without causing the generation of lumps in the mixture. Secondly, it maximizes the amount of free water which is present in the frozen product and which is uniformly distributed. This water is available to interact with microwave energy and hence raise the temperature and so uniformly melt the ice. By ensuring that the starch granules present in the frozen state of the product have only developed no more than 75% of the final thickness and the fat (to develop the cream-style taste and appearance) is present in a microemulsion of particles of a size less than 10 microns (and preferably less than 2 microns) it is ensured that a substantially homogeneous mixture of starch and oleaginous systems occurs in the freezing point depressed aqueous solution so that as a fully liquid system develops during heating in microwaves, a drinkable product results which does not need agitation (e.g. stirring) to give it an acceptable physical consistency.

BRIEF DESCRIPTION OF THE FIGURE

The FIGURE is a flow chart illustrating the commercial production of the tomato soup given in example I.

DETAILS OF SPECIFIC EMBODIMENTS

By way of non-limiting examples, the following give compositions of two soups in accordance with this invention.

    ______________________________________                                         Example I                                                                      Tomato Soup                                                                    per 150 ml unit                                                                Thickener levels                                                                          ColFlo 67             2.4 g                                         & types    Purity W              1.125 g                                                                        3.525 g                                       Both these products are ungelatinised waxy maize starches                      which are both acid stable and freeze/thaw stable.                                        Tomato Paste          10.80 g                                                  (32% solids)                                                        Creamer level                                                                             Hydrogenated vegetable oil in a                                                                      5.025 g                                       and type   spray-dried form on maltodextrin-                                              emulsifier and stabiliser.                                          Dispersants                                                                               Maltodextrin          3.00 g                                        (water activity                                                                           Sugar                 7.50 g                                        depressants)                                                                   Flavours                                                                       Salt                             1.65 g                                        Citric acid                      2.90 g                                        Spice Mix                        0.20 g                                        ______________________________________                                         Example II                                                                     Chicken Soup                                                                   Thickener levels                                                                          ColFlo 67             3.525 g                                       & types    Purity W              1.687 g                                                                        5.21 g                                        Creamer levels                                                                            Hydrogenated vegetable oil on a                                                                      3.09 g                                        & types    powdered maltodextrin carrier (The                                             ratio of oil to carrier can be altered                                         to give different types of creaminess)                                         Whey powder           1.5 g                                                                          4.59 g                                        Dispersants                                                                               Maltodextrin          3.0 g*                                        (water activity                                                                depressants)                                                                   Flavours   Yeatex (approx.)      0.3 g                                                    Onion powder          0.15 g                                                   Spice mix & Salt - to taste                                         ______________________________________                                           *The level of maltodextrin will be dependent on the type and level of         thickener used.                                                           

I claim:
 1. A process for manufacturing the precursor of a drinkable, starch-thickened, cream-style food product, heated from a frozen state without stirring in a microwave oven, which process comprises forming a homogeneous mixture of product flavouring components, spray dried creaming ingredient based on vegetable oil, granules of at least one acid stable, freeze/thaw stable starch and maltodextrin in water, heating the mixture to a temperature at which swelling of the starch granules will commence for a time to produce between 70% and 80% of the total swelling potential of the starch granules, dispensing the mixture into individual containers sufficient to contain the product while heated in a microwave oven and while subsequently consumed, and freezing the containers and dispensed mixture to a temperature of between -15° and -20° C. 